Befrigerating apparatus



l. MITCHELL REFRIGERATING APPARATUS Filed Aug. 8, 1919 Aug. 18, 1925. 1,549,918

A. I. MITCHELL REFRIGERATING APPARATUS Filed Aug. 8, 1919 3 Sheets-Sheet 2 7 a-Zf Patented Aug. 18, 1925.

UNITED STATES PATENT OFFICE.

ALEXANDER I. MITCHELL, OF MILTON, MASSACHUSETTS, ASSIGNOR TO STONE & WEB- STER, OF BOSTON, MASSACHUSETTS, A COPARTNERSHIP COMPOSED 0]? CHARLES A. STONE, EDWIN S. WEBSTER, HENRY G. BRADLEY, AND RUSSELL ROBB.

REFRIGERATING APPARATUS.

Application filed August 8, 1919. Serial No. 316,060.

To all whom it may concern:

Be it known that I, ALEXANDER I. MITCHELL, a citizen of the United States, residing at Milton, in the county of Norfolk and State of Massachusetts, have invented certain Improvements in Refrigerating Apparatus, of which the following description, in connection with the accompanying drawings, is a specification, like reference characters on the drawings indicating like parts in the several figures.

This invention relates to a refrigerating apparatus and is concerned particularly with that type of refrigerators intended for domestic use and in which the refrigerating action is produced without the use of ice.

A great many refrigerators of this general type have been proposed heretofore but they have met with only indifferent commercial success due to several reasons, among which may be mentioned particularly that the first cost of such refrigerators usually has been very high when compared with the cost of other! domestic types of refrigerators, that they usually have depended upon the use of chemicals which, if not properly handled, might produce serious damage, and further, that the proper operation of these refrigerators usually has required a degree of care and intelligence which could not be expected from the average servant who must look after such a piece of apparatus.

It is the chief object of the present invention to devise a refrigerating apparatus of the character above designated which will avoid these objections. That is, the invention aims to devise a refrigerating apparatus adapted particularly for domestic use, which will be very simple in construction, requiring neither ice nor condensers nor compressors, in which no explosive or dangerous chemicals are used, which can be economically manufactured and operated, in which an active circulation of air 'through the food compartment will be maintained so that odors from the food cannot collect to an undesirable degree, which will require a minimum of attention, and which will be practically fool-proof.

These, and other advantages and features of the invention, will be readily understood from the following description when read in connection with the accompanying drawings, in which,

Figure 1 is a view, partly in vertical cross section and partly in front elevation, showing a refrigerating apparatus embodying the present invention;

Fig. 2 is a vertical cross sectional view at right angles to the view shown in Fig. 1;

Fig. 3 is a horizontal cross sectional view on the line 3-3,, Fig. 2; and Fig. 4 is a horizontal cross sectional view on the line 4-4, Fig. 2.

It is well understood by those skilled in this art that if a vacuum is produced in a closed vessel containing a body of water, a cooling action will result due to the evaporation of a certain proportion of the water. That is, the exhaustion of the air from the vessel causes part of the water to vaporize, thus absorbing heat from the body of water due to the latent heat of vaporization. Only a very limited coolin efl'ect can be produced in this manner, owever. The

present invention utilizes this principle but, a

in addition, it provides means whereby an ample refrigerating effect can be produced economically and efficiently.

The apparatus shown comprises a suitable heat insulating casing 1, the walls of the casing being double and the space between them filled with ground cork, asbestos, mineral wool, or any other suitable heat insulating material. Access to the interior of the casing is provided by suitable doors, one of which is indicated at 2, the door or doors also being heat insulated. A food compartment having suitable shelves 3 is provided within the casing. Also mounted within the casing in immediate communication with the food compartment is a heat absorbing unit 4. This unit eon- SlS'iS of a container for water and it is so constructed that it presents a relatively large heat absorbing surface. For this purpose the unit comprises an upper header or tank-like receptacle 5, a lower header 5 much shallower than the upper header .5, and. a series of vertical tubes or pipes 7 that connect the upper and lower headers 5 and 6. The entire unit rests upon a series of blocks 8 which space the lower header from the bottom of the chamber in the easing. The upper header preferably has a series of vertical tubes therethrough as shown in Fig. 4 to provide increased heat absorbing surface. A drain pipe 9 leads from the lower header 8 through the bottom of the casing 1 and normally is closed by a cap 10. This unit is partially filled with water, as shown in the drawings, the height of the water being indicated by a. water gage 11.

A partial vacuum is maintained in the container el above the surface of the water therein by means of an exhaust apparatus comprising a pump 12, the intake side of which is connected with the upper part of the unit 4; by a pipe 13. Any suitable form of pump may be used but the form illustrated has proved very satisfasctory and therefore is preferably employed. This pump comprises a rotor 11 mounted within an eccentric chamber 15 formed in a suitable casing. The rotor contains four blades 16 which are mounted to slide radially in suitable slots or ways formed in the rotor, these blades being spring pressedoutwardly so that their outer edges are held constantly in engagement with the peripheral wall of the chamber 15. This wall is eccentric to the rotor from a point substantially at a and proceeding in the direction of rotation indicated by the arrow, to another point approx imately as indicated at 71; but between the points a and b the chamber is concentric with the rotor and is in contact therewith. The air enters the pump in the neighborhood of the point a and is exhausted or forced out of the chamber 15 through the pipe 16 in the neighborhood of the point D. The pump rotates in a bath of oil and provision is made, as is usual in this style of pump, for the entrance of a very small quantity of oil to the pump for lubricating and sealing purposes. Consequently, the construction of chamber just described provides a long sealing surface between the points I) and a which substantially reduces the leakage that otherwise would take place in the pump.

A check valve 17 is connected into the outlet pipe 16 and this pipe 16 discharges into a receptacle 18 which catches any oil that may be carried over and also serves as a mulfler. The pump preferably is driven very slowly, say, for instance revolutions per minute, and is operated by an electric motor 19 belted to a pulley 20 which operates through the reduction gears 21 to drive the pump. This slow speed operation is possible because the type of pump described can be constructed to give tight sealing and to have a large volumetric capacity, so that its percentage clearance is low. Slow speed operation is highly desirable in a domestic installation because of quiet operation.

When the apparatus is in operation the pump will exhaust the air and a certain quantity of water vapor from the space above the level of the liquid in the container 4. The reduction of pressure above the surface of the water will cause more of the water to vaporize thus lowering the temperature of the body of water in the unit 4. After a relatively short time, however, the maximum vacuum of which the apparatus is capable is produced and thereafter the vaporization takes place at only a relatively slow rate,too slow to produce. the. desired refrigerating action economically. The rate at which heat is absorbed will vary directly with the rate at. which the water in the unit 4 is evaporated, and I have discovered that the rate of vaporization can be greatly increased by providing a leak, so to speak. That is, means is provided for ad mitting a limited quantity of air into the unit.

This means consists of a pipe leading from a point in the food chamber of the refrigerator downwardly through the top of tliecontainer to a point in the water close to the bottom of the header A valve 2 is connected in this pipe and is adjustable to determine the rate at which air will be admitted into the container. In the apparatus shown a second air inlet is provided consisting of apipe 24 leading through a fitting 25 to which a bottle containing liquid to be chilled or frozen may be connected, the air being admitted to this pipe through a needle valve 26 by means of which a very fine adjustment of the rate of flow of the air can be made. This air inlet also is located within the casing, the two inlets preferably being positioned at a considerable distance apart so that they will take air from different parts of the chamber Air will find its way into the chamber around the doors and also'through a pipe 27 leading through the top of the casing 1 into a box 28 containing cotton, charcoal, or other air filtering material In case the fitting 25 is not used, all the air may be admitted to the unit through the pipe 22, the pipe 24 being omitted; and, if desired, the pipe 27 and filter 28 may also be omitted.

Inasmuch as the air enters the unit 4 at a point below the surface of the water, it comes in very intimate contact with the water and thus becomes substantially, if not entirely, saturated with water vapor. The result of this arrangement is, therefore. to draw continuously from the container 4- a. current of rarefied air, laden with water vapor. and thus to produce a rapid evaporation of the water and consequently, a rapid cooling action.

The rate at which the air drawn will vary with the speed of operation. of the pump, its efficiency, and the adjustment of the valve 23 and of the valve 26, if the latter is used.

I refrigerating action can be produced, however, by running the apparatus at a lower vacuum, and maintaining a higher air velocity, but the apparatus does not then operate at as high an efliciency. The problem, therefore is to find a suitable balance between the degree of vacuum to be maintained and the rate of flow of the air. Exhaustive experiments have indicated that for the usual size of domestic refrigerator an ample refrigerating action can be produced at a satisfactory efiiciency when the pump is driven at such a speed that it will deliver air at atmospheric pressure at the rate of about A; to cu. ft. per minute, the rate of intake of the air being so restricted that about two inches of absolute vacuum is maintained in the container 4.

Furthermore, in order to obtain a substantially complete saturation of the air with Water vapor it is desirable to have the submerged air orifices comparatively small and far enough below the surface of the Water so that the airremains in contact with the water as it bubbles up through it for a sufficient length of time to become saturated.

Satisfactory results have been obtained in the apparatus above described when two air inlets were located about five inches under the surface of the water, the inlets each being between and A of an inch in diameter.

It should be noted that free air is taken into the apparatus. That is, the air that is taken through the pipes 22 and 24 is the surrounding atmosphere at normal pressures as distinguished from compressed air. It will also be seen that the apparatus is of what may be termed an open circuit type. That is, the air is; taken directly from the atmosphere into the apparatus and exhausted again to the atmosphere, no return circuit being provided. This fact,.together with the fact that only air and water are used, makes the apparatus exceedingly simple and avoids the handling of any chemicals or other materials that might prove dangerous in the hands of a careless or unskilledperson.

In order to re-fill the apparatus when the supply of water in the unit 4 becomes lowered, a filling pipe 30 is led through the wall of the header 5 into a oint substantially at the bottom of the hea er and has a valve 31 connected to its outer end, to which also is connected a flexible hose 32. If the end of this hose is submerged in a body of water, the vacuum in the unit will draw this water through the hose into the unit and the refilling operation can thus be very conveniently performed. By watching the gage 11 the attendant can determine when the refilling operation is necessary and when it has been carried to the desired point. A barometric gage 33, of simple form, is connected to the apparatus to show the degree of vacuum maintained therein.

lo order to make the apparatus substantially automatic in operation, a thermostatic control for the motor 19 is provided. This controlling apparatus may be of any one of several types obtainable on the market, that illustrated being known commercially as the Sarco temperature regulator. This apparatus comprises a thermostatic unit 34;, secured in the top of the casing 1 and extending through one of the tubes in the upper header 5, an electric switch 35 arranged to be operated by the thermostat 34, and connections 37 leading down the back of the casing 1 from this switch to the motor 19.

This apparatus is responsive automatically 1 to changes in temperature in the refrigerator to switch the current on to the motor 19' When'the temperature rises above a predetermined point and to cut off the current and stop the motor when the temperature has dropped to a predetermined point. The points at which the current is thrown on and off the motor may be varied at will by suitable adjustments provided in the apparatus.

The operation of the apparatus has been so fully described hereinbefore that any further statement of operation is believed to be unnecessary. It will readily be understood that slnce the apparatus is exceedingly simple in construction, it can be very economically manufactured, that is practically fool-proof, the only active elements employed to eli'ect the refrigerating action being air and water, and that the apparatus requires no attention other than to keep it properly filled with water. Inasmuch as an active circulation of air is maintained through, the food compartment there is no opportunity for odors from the food to collect in the refrigerator and it thus automatically maintains itself in a clean and sanitary condition so far as ventilation can produce this result.

The pump construction above described also is superior to any heretofore proposed of which I am aware for the purpose of an apparatus of this character. That is, it is desirable, as above described, in this apparatus to maintain a comparatively high vacuum while still handling a considerable quantity of air. The pump herein described gives far more favorable results than I have been able to produce with any other pump and the improvedresults appears to be due to the fact that the concentric wall in contact with the rotor substantially reduces the leakage between the high and low pressure sides of the pump.

hat is claimed as new is:

1. A refrigerating apparatus comprising, in combination, a heat insulating casing having a food compartment therein, a heat absorbing unit in said casing for absorbing heat from said compartment, said unit comprising a container having water therein, means for maintaining a partial vacuum in said container, means for admitting air from said compartment into said container at a point below the surface of the water therein, a pipe admitting air into said compartment at a point relatively remote from the point at which the air is taken from said compartment and means for filtering the air entering the compartment through said pipe.

2. A domestic refrigerator comprising in combination a heat-insulated casing enclosing a food compartment; a closed water container having a heat absorbing surface exposed within said compartment; a rotary suction pump of relatively large volumetric capacity connected to withdraw air and water vapor from said.c0nta.iner, and discharge it to atmosphere; means for admitting air at a restricted rate to the interior of said container in intimate contact with the water therein; and a motor for driving said pump.

3. A refrigerating apparatus comprising, in combination, a heat insulating casing having a food compartment therein, a heat absorbing unit in said casing for absorbing heat from said compartment, said unit comprising a container for a body of water, means for conducting air from said food compartment into said container at a substantial distance below the surface of the water in said container, means for restricting the flow of air so admitted to the container, and an exhaust pump connected with the space in said container above the water therein and operative to maintain a high vacuum in said container notwithstanding said restricted admission of air into the container.

4. A domestic refrigerator comprising in combination a heatinsulated easing enclosing a food compartn'ient; a closed water container having a heat absorbing surface exposed within said eompartment; a rotary sliding blade pump connected to withdraw air and water vapor from said container, and discharge it to atmosphere; means for admitting air at a restricted rate to the interior of said container in intimate contact with the water therein; and a motor for driving said pump.

In testimony whereof I have signed my name to this specification.

ALEXANDER I. MITCHELL. 

